A269823 Number of n X 2 0..4 arrays with some element plus some horizontally, diagonally, antidiagonally or vertically adjacent neighbor totaling four exactly once.

5, 216, 3096, 39784, 462680, 5145736, 55265336, 580002280, 5978552216, 60784629832, 611189228792, 6090202880680, 60229576820312, 591855697435912, 5784216137341880, 56261693581866856, 544976552619855128

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 10*a(n-1) + 47*a(n-2) - 336*a(n-3) - 1416*a(n-4) - 864*a(n-5) - 144*a(n-6) for n>7.

Empirical g.f.: x*(5 + 166*x + 701*x^2 + 352*x^3 - 1016*x^4 - 480*x^5 + 720*x^6) / (1 - 5*x - 36*x^2 - 12*x^3)^2. - Colin Barker, Jan 29 2019

Example

Some solutions for n=4:
..4..2. .2..0. .1..1. .3..3. .1..4. .4..2. .1..1. .3..3. .2..4. .2..3
..1..4. .0..3. .4..2. .2..2. .2..0. .1..1. .2..0. .4..4. .3..0. .0..4
..1..2. .2..0. .3..0. .4..4. .0..0. .4..2. .1..2. .2..1. .3..3. .1..1
..2..0. .4..3. .3..0. .4..4. .1..2. .3..2. .1..4. .0..2. .2..0. .2..1

Crossrefs

Column 2 of A269829.

Sequence in context: A048433 A270870 A144796 * A206457 A291806 A119657

Adjacent sequences: A269820 A269821 A269822 * A269824 A269825 A269826

Keyword

nonn

Author

R. H. Hardin, Mar 05 2016

Status

approved